CN107576679B - Method for calibrating local cooling speed of electroslag ingot in process of producing high-speed steel through electroslag remelting - Google Patents
Method for calibrating local cooling speed of electroslag ingot in process of producing high-speed steel through electroslag remelting Download PDFInfo
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Abstract
The invention belongs to the technical field of metallurgy, and particularly relates to a method for calibrating local cooling speed of an electroslag ingot in an electroslag remelting high-speed steel production process, in particular to a method for accurately controlling quality of carbide of high-speed steel by calibrating the local cooling speed of the electroslag ingot of the high-speed steel. The quantitative relationship between the cooling speed and the carbide of the electroslag ingot produced by electroslag remelting is researched, and the quantitative relationship curve and the relational expression between the cooling speed and the carbide characteristic of the electroslag ingot are obtained by counting and calculating the carbide characteristic at different cooling speeds; the cooling speed during local solidification is effectively determined according to the carbide mesh distance of the electroslag ingot; therefore, in the actual production of high-speed steel, the cooling speed during local solidification can be changed directly by adjusting the technological parameters of electroslag remelting, and the electroslag steel ingot with the required carbide quality requirement can be obtained.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for calibrating local cooling speed of an electroslag ingot in an electroslag remelting high-speed steel production process, in particular to a method for accurately controlling quality of carbide of high-speed steel by calibrating the local cooling speed of the electroslag ingot of the high-speed steel.
Background
The electroslag remelting method is a main method for preparing high-quality high-speed steel, and has the advantages of less non-metallic inclusions, high metal purity, uniform crystal structure in the center of a steel ingot, compact structure, good surface quality of the steel ingot and the like.
The high-speed steel has high carbon saturation, the quantity of eutectic carbides is large, the carbides form a continuous net to divide a matrix, so that the plasticity of the steel is poor, the initial carbide in the high-speed steel starts to decompose at a high temperature and is difficult to completely decompose, and microcracks are easy to generate in various steels of the high-speed steel. Meanwhile, because the alloy content of the high-speed steel is high and the mushy zone is wide, the segregation of the carbide is more serious, and the problems of higher unevenness of the carbide, larger particle size of the carbide and the like are caused. The distribution uniformity, particle size, type, quantity and the like of carbides in the high-speed steel directly influence the quality and the service performance of the high-speed steel, the characteristics of the carbides are related to heat treatment and hot working deformation, more importantly, the cast structure, and particularly, the unevenness and the particle diameter of the cast eutectic carbides directly determine the subsequent processing performance. The local cooling speed of the electroslag ingot in the electroslag remelting process plays a decisive role in the carbide quality of the steel ingot. The larger the local cooling speed is, the larger the nucleation supercooling degree is, the better the solidification nucleation is, and the carbide particles in the solidification process of the high-speed steel are finer and more uniformly distributed.
Research shows that increasing the cooling speed of high-speed steel can promote the peritectic reaction L + delta → gamma, so that delta ferrite is quickly and completely wrapped by austenite, the diffusion speed of elements is reduced, the component segregation is inhibited, and the carbide mesh distance is reduced. Since the distance between the solid-liquid two-phase regions is difficult to change, it is important to increase the local solidification rate to reduce the variation of the carbide network pitch of the high-speed steel. The relationship between the local solidification time of the solid-liquid two-phase region and the width, the local solidification speed, the secondary dendrite spacing and the like of the two-phase region is as follows:
LST＝X/Vr
logd＝k1+k2logLST
in the formula: LST is local solidification time, s; x is the distance of a solid-liquid two-phase area, and is mm; vr is the local solidification speed, mm/s, G is the liquid phase temperature gradient, K/mm; rc is local cooling rate, K.s-1(ii) a d is the secondary dendrite spacing, mm; k1, k2 are constants related to the material properties.
Generally, the quality of carbide is represented by the carbide mesh spacing of the electroslag ingot, and the smaller the carbide mesh spacing is, the smaller the unevenness of the carbide is, and the better the quality of the electroslag ingot is. However, the height of the liquid metal cylinder end of the molten pool is reduced or even disappears due to the low cooling speed, and surface quality defects such as slag ditches, accretions and the like appear on the surface of the steel ingot. Therefore, the reasonable control of the local cooling speed of the electroslag ingot in the electroslag remelting process has a decisive role in producing high-quality high-speed steel electroslag ingots. However, the upper part of the metal molten pool is always covered by the liquid slag pool in the whole electroslag remelting production process, and the lower part and the periphery of the metal molten pool are positioned in the crystallizer; meanwhile, the slag bath and the metal bath are always kept at high temperature of 1300-1900 ℃, so that the cooling speed of the electroslag ingot is difficult to measure. On the other hand, a metallurgy worker realizes the control of the solidification structure of the electroslag ingot by adjusting process parameters such as a slag system, a slag quantity, a current and a voltage, but does not realize quantitative representation of the process improvement effect, so that the accurate control of the quality of the electroslag ingot is difficult to realize. Through years of research, the applicant finds that the accurate calibration of the local cooling speed of the electroslag ingot under different process conditions is important for optimizing an electroslag remelting process system and the quality of high-speed steel carbide. However, the applicant looks up a large amount of data to find that at present, no effective method is available for scholars at home and abroad to calibrate the local cooling speed of the electroslag ingot in the production process so as to guide the production of high-quality and high-speed steel; therefore, accurate calibration of the local cooling rate of the electroslag ingot is a problem to be solved urgently for accurate control of the quality of high-speed steel carbide.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a method for calibrating the local cooling speed of an electroslag ingot in the process of producing high-speed steel by electroslag remelting, which is a method for improving the quality of carbide of the high-speed steel electroslag ingot by correspondingly adjusting the electroslag process parameters in production practice through accurately calibrating the local cooling speed of the electroslag ingot; the method is used for calibrating the local cooling speed of the electroslag ingot in the process of producing high-speed steel by electroslag remelting, and particularly is used for measuring the corresponding relation between the characteristics of high-speed steel carbide and the local cooling speed of the high-speed steel carbide, researching the quantitative relation between the cooling speed of the electroslag ingot produced by electroslag remelting and the carbide, and obtaining a quantitative relation curve and a relational expression between the cooling speed of the electroslag ingot and the characteristics of the carbide by counting and calculating the characteristics of the carbide at different cooling speeds; the cooling speed during local solidification is effectively determined according to the carbide mesh distance of the electroslag ingot; therefore, in the actual production of high-speed steel, the cooling speed during local solidification can be changed directly by adjusting the technological parameters of electroslag remelting, and the electroslag steel ingot with the required carbide quality requirement can be obtained.
In order to achieve the purpose, the method for calibrating the cooling speed of the electroslag ingot for producing high-speed steel by electroslag remelting comprises the following steps: firstly, measuring the carbide net distance of a high-speed steel sample, and then determining the local cooling speed of the high-speed steel sample through a quantitative relation between the carbide characteristics of the high-speed steel at different cooling speeds and the local cooling speed.
The method for determining the quantitative relational expression comprises the following steps: obtaining a full-melting sample of the high-speed steel after the sample is solidified at different cooling speeds by using an ultrahigh-temperature laser confocal microscope; grinding and polishing the sample, and finally observing a microstructure image by using a scanning electron microscope; and (3) establishing a corresponding quantitative relation curve between the carbide mesh distance obtained from the back scattering experimental result of the scanning electron microscope and the cooling speed used by the ultra-high temperature laser confocal microscope, and measuring the carbide mesh distance of the high-speed steel according to the requirement through the curve to determine the cooling speed of the carbide mesh distance.
The method for determining the quantitative relation comprises the following steps: firstly, cutting n samples (n is an integer not less than 20) of high-speed steel, wherein the test specification is phi 7mm multiplied by 2.5mm, and grinding and polishing to remove surface oxides; n groups of cooling speed experiments are respectively designed; then, obtaining a full-melting sample after the sample is solidified at different cooling speeds by using an ultrahigh-temperature laser confocal microscope; finally, grinding and polishing the full-melting sample, observing a microstructure image by using a scanning electron microscope, and backscattering the full-melting sample by using the electron microscope to obtain the carbide mesh distance of the full-melting sample; and establishing a corresponding relation between the average carbide mesh distance obtained from the scanning electron microscope back scattering experimental result and the cooling speed used by the ultra-high temperature laser confocal microscope.
Preferably, the high-speed steel is M42 high-speed steel, and the quantitative relationship is as follows:
y-26.08 x +70.22(0< x <1.0), y-3.36 x +49.56(1.0< x <4.0) (applicable only to M42 high speed steel)
In the formula: x is the cooling speed of the position during solidification, unit, DEG C/s; y is the high speed steel carbide mesh spacing at that location in μm.
The quantitative relational expression of other high-speed steels is the same as the method for determining the quantitative relational expression of M42 high-speed steel according to the present invention.
The ultrahigh-temperature laser confocal microscope is preferably a VL2000DX-SVF17SP ultrahigh-temperature laser confocal microscope; the method is mainly used for real-time high-definition observation and analysis of material organization structure change melting solidification crystallization; the microscope high-temperature furnace heating mode has the advantages that the infrared light collection method is adopted, the heating and cooling speed can be high, the heating and cooling processes can be controlled according to the program arbitrary setting, the temperature can be rapidly raised and lowered, the temperature can be slowly raised and lowered, the microscope high-temperature furnace can work within the temperature change range of 20-1700 ℃, and a sample can be cooled at a constant cooling speed.
The scanning electron microscope is preferably JSM6480LV Scanning Electron Microscope (SEM); the functional characteristics are as follows: the surface appearance of different materials is observed, a scanning electron microscope is the optimal choice for massive samples which are inconvenient to destructively treat, qualitative and semi-quantitative analysis can be carried out on various elements by matching with an energy spectrometer, and the surface characteristics of heterogeneous organic materials and inorganic materials in a micrometer range can be observed and detected by using an electron back scattering diffraction system of the system.
The invention has the beneficial effects.
In the exploration process of the method for improving the quality of the high-speed steel carbide, the cooling speed of the high-speed steel electroslag ingot and the carbide are found to have a certain quantitative relation, if the corresponding relation of the cooling speed and the carbide can be determined, the influence of the solidification rate on the carbide of the electroslag ingot in actual production can be fully understood, and the optimization of the production process of the high-speed steel can be guided, so that the quality and the performance of the electroslag ingot can be improved. Therefore, if the quantitative relation between the cooling speed and the carbide characteristics can be determined, the cooling speed can be determined according to the carbide characteristics of the produced electroslag ingot, and then the process parameters are adjusted to guide production.
The method for improving the quality of the high-speed steel carbide, which is disclosed by the invention, has the following outstanding advantages: (1) the method can effectively judge the effectiveness of the process improvement means and realize the accurate control of the quality of the carbide of the high-speed steel product remelted by electroslag; the local cooling speed of the steel ingot in the electroslag remelting process is changed by adjusting process parameters, so that carbide particles of high-speed steel produced by electroslag remelting are finer and more uniformly distributed, and the quality of the high-speed steel is improved; (2) the method is safe and simple, and solves the problem that the local cooling speed of the molten steel is difficult to determine in the electroslag remelting production process; (3) the method is suitable for all high-speed steel produced by an electroslag remelting process; (4) the method for calibrating the cooling rate of the electroslag remelting high-speed steel can detect the effectiveness of the process (5), and a cooling rate-carbide morphology curve obtained by a few experiments is suitable for the whole steel ingot.
Drawings
FIG. 1 is a graph showing the variation of the average mesh distance of M42 high-speed steel carbide with the cooling speed.
FIG. 2 is a temperature-time variation curve with a cooling rate of 4 ℃/s in the temperature raising and lowering procedure of the ultra-high temperature confocal laser microscope in example 1.
FIG. 3 is a back-scattered image X100 of samples obtained by high temperature confocal laser scanning microscopy at different cooling rates.
FIG. 4 is a scanning electron microscope for observing the mesh spacing of M42 high-speed steel carbide measured in example 1.
FIG. 5 is a scanning electron microscope for observing the mesh spacing of M42 high-speed steel carbide measured in example 2.
FIG. 6 is a scanning electron microscope for observing the mesh spacing of M42 high-speed steel carbide measured in example 3.
FIG. 7 is a scanning electron microscope for observing the mesh spacing of M42 high-speed steel carbide measured in example 4.
Detailed Description
The present invention will be further described with reference to the following specific examples.
Example 1.
The principle of the cooling speed calibration method for producing the electroslag ingot by electroslag remelting is as follows (taking M42 high-speed steel as an example): firstly, cutting 20 samples of M42(W2Mo9Cr4Co8) high-speed steel, wherein the specification of the samples is phi 7mm multiplied by 2.5mm, and grinding and polishing to remove surface oxides; 20 sets of cooling rate experiments were designed, and the experimental groups are shown in table 1. Obtaining a full-melting sample after the sample is solidified at different cooling speeds by using an ultrahigh-temperature laser confocal microscope; and (3) grinding and polishing the sample, and finally observing a microstructure image by using a scanning electron microscope, wherein the mesh distance of carbide obtained by backscattering the full-melting sample by the electron microscope is shown in a table 2, and the backscattering image of the full-melting sample is shown in a table 3, wherein (a) is 0.5 ℃/s, (b) is 0.75 ℃/s, (c) is 1.00 ℃/s, (d) is 2.5 ℃/s, and (e) is 4 ℃/s. Establishing a corresponding relation between the average carbide mesh distance obtained from the back scattering experiment result of the scanning electron microscope and the cooling speed used by the ultra-high temperature laser confocal microscope, wherein the relation is as follows:
y＝-26.08x+70.22(0<x<1.0)，y＝-3.36x+49.56(1.0<x<4.0)
in the formula: x is the cooling speed at the solidification of the position, unit, DEG C/s; y is the average carbide spacing in μm at that location.
The quantitative relation curve of the carbide mesh spacing and the cooling speed of the M42 high-speed steel electroslag ingot is shown in a figure 1.
And obtaining the corresponding relation between the cooling speed and the carbide characteristics. In practical production application, the cooling speed of the position during solidification can be obtained according to the measured carbide mesh distance of the high-speed steel electroslag ingot. The carbide mesh spacing of the M42 high-speed steel electroslag ingot is related to the cooling speed, and the figure is shown in figure 1.
Table 1 ultra-high temperature laser confocal microscope cooling speed experimental group.
Table 2 average carbide spacing of the fully melted samples obtained by electron microscopy back scattering.
The operating method of the ultra-high temperature laser confocal microscope used by the invention is as follows:
step one, setting heating and cooling programs according to experimental needs, and preserving heat for 60 seconds after the temperature reaches the liquidus temperature according to the liquidus temperature of the known steel grade, so as to ensure that the sample is completely melted. The temperature profile at a cooling rate of 4 ℃/s over time is shown in FIG. 2.
And step two, placing the prepared sample in an alumina crucible, placing the crucible in a heating furnace, laying the crucible flat, and covering a furnace cover.
And step three, operating HiTOS-D software in a computer, finding a surface image of the sample by adjusting the focal length of the microscope, and editing a program according to an experimental scheme.
Step four, according to the specified steps of the equipment, vacuumizing the heating furnace; and after the vacuum pumping is finished, closing the valve of the vacuum pump, opening the argon valve and introducing argon.
And step five, repeating the steps twice, and clicking a start button to operate the program after argon is introduced.
And step six, only changing the cooling speed, and respectively carrying out different experiments by adopting the same experimental process and other data to obtain the solidified full-melting samples with different cooling speeds. Metallographic samples were prepared from the all-molten samples, and after observation under a scanning electron microscope, metallographic photographs were obtained, and the distances between the carbide networks at different cooling rates were measured by Image analysis software (preferably Image-Pro-Plus) as shown in Table 2.
Example 2.
Electroslag remelting is used for producing an M42 high-speed steel ingot with 1140mm long and 200mm radius, and the process parameters are shown in Table 3. And a platinum rhodium thermocouple (thermocouple position: height is 600mm, distance is 15mm from the wall of the crystallizer) is pre-embedded in the crystallizer, and the cooling speed is about 0.72 ℃/s. After electroslag remelting is finished, making the high-speed steel at the embedded thermocouple into a sample, polishing the sample, observing the sample by using a scanning electron microscope, and performing computational analysis on an Image of the sample by using Image analysis software (preferably Image-Pro-Plus) to obtain the average mesh distance of carbide of the sample, wherein the average mesh distance of the carbide is 49.09 mu m; JSM6480LV Scanning Electron Microscope (SEM) observation of the measured M42 high speed steel carbide mesh spacing, see fig. 4; the quantitative plot of average mesh distance of the M42 carbide versus cooling rate was carried in, where the cooling rate was approximately 0.75 deg.C/s, which is close to the experimental results.
TABLE 3 Process parameters for electroslag remelting of M42 high speed steel with 1140mm long ingot and 200mm radius
| Crystallizer diameter (mm) | 400 |
| Electrode diameter (mm) | 139 |
| Furnace mouth voltage (V) | 35 |
| Current (A) | 7500 |
| Melting speed (kg/min) | 4.35 |
| Crystallizer wall thickness (mm) | 16 |
Example 3.
The electroslag remelting produces M42 high-speed steel with an ingot length of 1230mm and a radius of 180mm, and the process parameters are shown in Table 4. And a platinum rhodium thermocouple (thermocouple position: height is 600mm, and distance is 55mm from the wall of the crystallizer) is pre-embedded in the crystallizer, and the cooling speed at the position is measured to be about 2.62 ℃/s. Preparing a sample from the high-speed steel at the pre-embedded thermocouple, grinding and polishing the sample, observing the sample by using a scanning electron microscope, and calculating and analyzing an Image of the sample by using Image-Pro Plus Image analysis software to obtain the average mesh distance of carbide of the sample, wherein the average mesh distance of the carbide is 42.84 micrometers; JSM6480LV Scanning Electron Microscope (SEM) observation of the measured M42 high speed steel carbide mesh spacing, see fig. 5; the quantitative relationship curve of the average grid distance of the M42 high speed steel carbide and the cooling rate is brought into the curve, wherein the cooling rate is about 2.52 ℃/s, which is similar to the experimental result.
TABLE 4 Process parameters for electroslag remelting for producing M42 high-speed steel with 1230mm long ingot and 180mm radius
Example 4.
Electroslag remelting is used for producing M42 high-speed steel with an ingot length of 1140mm and a diameter of 200mm, and the process parameters are shown in Table 5. And a platinum rhodium thermocouple (the thermocouple position is 600mm in height and 75mm away from the wall of the crystallizer) is pre-embedded in the crystallizer, and the cooling speed of the thermocouple obtained by measuring temperature in the production process is about 3.18 ℃/s. Taking high-speed steel with M42 output and pre-buried in a thermocouple to prepare a sample, polishing the sample, observing the sample by using a scanning electron microscope, and performing calculation analysis on an Image of the sample by using Image-Pro Plus Image analysis software to obtain the average mesh distance of carbide of the sample to be 38.84 microns; JSM6480LV Scanning Electron Microscope (SEM) observation of the measured M42 high speed steel carbide mesh spacing, see fig. 6; the average grid distance of the M42 carbide was brought into a quantitative relationship with the cooling rate, which here was about 3.11 ℃/s, which was similar to the test results.
TABLE 5 Process parameters for electroslag remelting of M42 high speed steel with 1140mm long ingot and 200mm radius
| Crystallizer diameter (mm) | 400 |
| Electrode diameter (mm) | 139 |
| Furnace mouth voltage (V) | 34 |
| Current (A) | 7500 |
| Melting speed (kg/min) | 4.33 |
| Crystallizer wall thickness (mm) | 16 |
Example 5.
The electroslag remelting produces M42 high-speed steel with an ingot length of 1230mm and a diameter of 180mm, and the process parameters are shown in Table 6. And a platinum rhodium thermocouple (thermocouple position: height is 600mm, distance is 25mm from the crystallizer wall) is pre-embedded in the crystallizer, and the cooling speed is measured to be about 0.98 ℃/s. Taking high-speed steel inserted into an M42 high-speed steel pre-buried thermocouple, preparing a sample, polishing, observing by using a scanning electron microscope, and performing computational analysis on an Image of the sample by using Image-Pro Plus Image analysis software to obtain the average mesh distance of carbide of the sample to be 44.52 microns; JSM6480LV Scanning Electron Microscope (SEM) observation of the measured M42 high speed steel carbide mesh spacing, see fig. 7; the quantitative relationship curve of the average grid distance of the M42 high-speed steel carbide and the cooling speed is brought into, wherein the cooling speed is about 1.03 ℃/s and is similar to the experimental test result.
TABLE 6 Process parameters for producing M42 high-speed steel with 1230mm long ingot and 180mm radius by electroslag remelting
| Crystallizer diameter (mm) | 360 |
| Electrode diameter (mm) | 118 |
| Furnace mouth voltage (V) | 33 |
| Current (A) | 7200 |
| Melting speed (kg/min) | 4.15 |
| Crystallizer wall thickness (mm) | 16 |
Example 6.
According to the requirements of certain alloy tool factories, a batch of M42 high-speed steel with the average carbide net distance of less than 36 μ M needs to be produced. The cooling speed corresponding to the net distance is predicted to be about 4.1 ℃/s through a quantitative relation formula of the net distance of the high-speed steel carbide and the cooling speed. The production process of the embodiment 4 is improved, the ingot drawing electroslag remelting process is used for producing high-speed steel, secondary aerial fog cooling is applied to the drawn electroslag ingot, the cooling speed of the electroslag ingot is accelerated, and other process parameters are unchanged. After the process is adjusted, high-speed steel with the same specification is produced, platinum-rhodium thermocouples are pre-embedded in the crystallizer at the same position, and the cooling speed at the position is measured to be increased to 4.03 ℃/s from 3.11 ℃/s of the original embodiment 4. Through the corresponding relation between the cooling speed of the M42 high-speed steel and the carbide characteristics, the mesh distance of the carbide is predicted to be reduced to 35.59 mu M from 38.84 mu M of the original embodiment 4, the high-speed steel inserted into a M42 high-speed steel pre-buried thermocouple is taken to be made into a sample, the sample is polished and observed by a scanning electron microscope, and the Image is calculated and analyzed by Image-Pro Plus Image analysis software to obtain the average mesh distance of the carbide of 35.62 mu M; the quantitative plot of average mesh distance of M42 high speed steel carbides versus cooling rate was carried in, where the cooling rate was approximately 3.98 ℃/s.
Example 7.
According to the requirements of certain alloy tool factories, a batch of M42 high-speed steel with the average carbide net distance of less than 38 mu M needs to be produced. The cooling speed corresponding to the net distance is predicted to be about 3.4 ℃/s through a quantitative relation formula of the net distance of the high-speed steel carbide and the cooling speed. The production process of the embodiment 4 is improved, the amount of slag in electroslag remelting is increased from 50kg to 55kg, so that the cooling speed of an electroslag ingot is increased, and other parameters are unchanged. After the adjustment process, high-speed steel with the same specification is produced, platinum-rhodium thermocouples are embedded in the crystallizer at the same position, and the cooling speed at the position is measured to be increased to 3.34 ℃/s from 3.11 ℃/s of the original embodiment 4. Predicting that the net distance of the carbide at the position is reduced to 37.79 mu M from 38.84 mu M of the original embodiment 4 by using a corresponding relation formula of the cooling speed and the carbide characteristics of the M42 high-speed steel, taking the high-speed steel at the position where the produced M42 high-speed steel is embedded with a thermocouple, preparing a sample, polishing the sample, observing the sample by using a scanning electron microscope, and performing calculation analysis on the Image by using Image-Pro Plus Image analysis software to obtain the average net distance of the carbide of 38.02 mu M; the quantitative plot of average mesh distance of M42 high speed steel carbides versus cooling rate was carried in, where the cooling rate was approximately 3.36 ℃/s.
Claims (2)
1. A method for calibrating the local cooling speed of an electroslag ingot in the process of producing high-speed steel by electroslag remelting is characterized by comprising the following steps: firstly, measuring the carbide net distance of a high-speed steel sample, and then determining the local cooling speed of the high-speed steel sample through a quantitative relation between the carbide characteristics of the high-speed steel and the local cooling speed under the condition of different cooling speeds;
the high-speed steel is M42 high-speed steel;
the quantitative relation between the carbide characteristic of the M42 high-speed steel and the local cooling speed is as follows: y is-26.08 x +70.22, x is more than 0 and less than 1.0, y is-3.36 x +49.56, and x is more than 1.0 and less than 4.0;
in the formula: x is the cooling speed of the position during solidification, and the unit ℃/s; y is the high-speed steel carbide net distance of the position, unit, mu m;
the method for determining the quantitative relational expression comprises the following steps: obtaining a full-melting sample of the high-speed steel after the sample is solidified at different cooling speeds by using an ultrahigh-temperature laser confocal microscope; grinding and polishing the full-melting sample, and observing a microstructure image by using a scanning electron microscope; and establishing a corresponding quantitative relation curve between the carbide mesh distance obtained from the scanning electron microscope back scattering experimental result and the cooling speed used by the ultra-high temperature laser confocal microscope.
2. The method for calibrating the local cooling rate of an electroslag ingot in the process of producing high-speed steel through electroslag remelting according to claim 1, wherein the method for determining the quantitative relational expression specifically comprises the following steps:
firstly, cutting n samples of high-speed steel, wherein n is an integer not less than 20, the test specification is phi 7mm multiplied by 2.5mm, and grinding and polishing to remove surface oxides; n groups of cooling speed experiments are respectively designed; then, obtaining a full-melting sample after the sample is solidified at different cooling speeds by using an ultrahigh-temperature laser confocal microscope; finally, grinding and polishing the full-melting sample, observing a microstructure image by using a scanning electron microscope, and backscattering the full-melting sample by using the electron microscope to obtain the carbide mesh distance of the full-melting sample; and establishing a corresponding relation between the average carbide mesh distance obtained from the scanning electron microscope back scattering experimental result and the cooling speed used by the ultrahigh-temperature laser confocal microscope.
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